One reason sessions spring up is because very few pubs these days still have function rooms, and those which do tend to charge a lot more than they used to.

Another reason is that it's a different way of making music, and makes for a different type of music.

I doubt if a session anywhere has ever killed a folk club. Sometimes where a folk club has died, a session succeeds it, as a way of keeping the music alive as much as anything. That happened to us in Harlow when for various reasons, mostly financial, it became impossible to keep a folk club going.

One of the best clubs I know, the Clap and Smile in Stortford, works as a tunes-and-songs session in the bar fortnightly, and once a month or so it runs as a club in the function room with paid guests and a couple of floor spots, and that strikes me as a pretty good way of combining the two styles.

I see there've been posts in this thread from New Zealand and the USA. I somehow doubt if that'd happen on the folk on 2 website. I haven't been there in some time - it seems a bit clunky compared to here and it's got restrictive rules such as forbidding people from including a link in their posts and stuff like that. And no realm life to it that I could see. Maybe it's got better.